THE FORENSIC DIAGNOSTIC PLAYBOOK

Practical Application Procedures for Common Hardware Failure Modes

Document ID: TOS-DIAG-PLAY-001 Version: 1.2

Section_1: THE “DOA” PROTOCOL (DEAD ON ARRIVAL)#

Scenario: Console is connected to power. No LED, no fan, zero signs of life.

STAGE_1: 01 // External Supply Validation#

• The Check: Measure the output of the AC Adapter or internal PSU.
• The Threshold: Voltage must be within ±5% of the rating.
• Practical Note: Many “Third Party” SNES/Mega Drive power bricks fail under load. If the voltage drops by >2V when the console is switched ON, the supply is functionally exhausted.

STAGE_1: 02 // The Protection Layer (Tier 1)#

• The Check: Check the internal fuse (e.g., PicoFuse on SNES/PS1, thermal fuse on Saturn).
• Forensic Clue: If the fuse is open (no continuity), DO NOT REPLACE YET.
• Investigation: Measure the resistance from the downstream side of the fuse to Ground.
  • If $<100 \Omega$ on a 5V line, a “Hard Short” exists.
  • Replacing the fuse without finding the short will result in an immediate second blow or substrate damage.

STAGE_1: 03 // Regulation Analysis (Tier 2)#

• The Check: Probe the output pin of the main regulator (e.g., Pin 3 of the 7805).
• The Logic: If 9V enters but 0V exits, and there is no short-to-ground, the regulator is internally open.
• Practical Note: On the Sega Dreamcast, ensure the 12V and 5V rails are present at the PSU-to-Motherboard pins. If 12V is missing, the GD-ROM will never initialise.

Section_2: THE “BLACK SCREEN” PROTOCOL (LOGIC PARALYSIS)#

Scenario: Power LED is ON. Voltage rails are stable. No video or audio output.

STAGE_2: 01 // The Master Clock Verification#

• The Tool: Oscilloscope (100MHz).
• The Check: Probe the output of the Master Crystal (XTAL).
• Forensic Clue: No sine wave = No logical heartbeat. The CPU is “dead in the water.”
• Target: NES (21.47 MHz), Mega Drive (53.69 MHz), PS1 (67.73 MHz).

STAGE_2: 02 // The Reset Handshake#

• The Check: Monitor the /RESET pin of the CPU during power-on.
• The Standard: The pin should start Low (0V) and flip to High (5V) after approx. 100ms.
• Failure Mode: If the Reset pin stays Low, the Reset IC or a failing RC Circuit is keeping the system in a permanent coma.

STAGE_2: 03 // Address/Data Bus Activity#

• The Tool: Logic Analyser or Oscilloscope.
• The Check: Probe Address lines A0-A7 on the BIOS chip.
• Analysis: If the lines are flat (no toggling), the CPU has failed to initiate the “Boot Vector” read.
• The Fix: Reflow the BIOS and CPU pins. Oxidation on high-pin-count ASICs is the leading cause of this “Ghost Failure.”

Section_3: THE “GARBAGE VIDEO” PROTOCOL (DATA CORRUPTION)#

Scenario: System boots. Audio is present. Video shows scrambled sprites, “jailbars,” or vertical lines.

STAGE_3: 01 // VRAM Isolation#

• The Check: Inspect sprite vs. background corruption.
• Logic A: Corruption in sprites only (objects moving) = S-Bus / Sprite RAM failure.
• Logic B: Corruption in static backgrounds = B-Bus / Background RAM failure.
• The Fix: Replace the identified RAM IC or reflow the traces between the RAM and the GPU/PPU.

STAGE_3: 02 // Trace Rot Forensics (Neo Geo / Mega Drive)#

• The Check: Continuity sweep between the Cartridge Slot and the Graphics ICs.
• Forensic Clue: If specific vertical lines stay static on screen, a single data bit (D0-D15) is likely severed.
• The Fix: Restore the bit-path with 0.1mm Enameled Wire (TOS-WIKI-REF-006).

STAGE_3: 03 // Video Encoder Filter Failure#

• Symptom: “Rainbowing,” blurred edges, or lost sync.
• The Check: Inspect the coupling capacitors on the RGB/Composite output lines.
• Threshold: If ESR is $>5 \Omega$ on a 100uF output cap, the signal is being “choked.”
• Practical Note: On the Sega Mega Drive, the CXA1145 encoder requires a 75-ohm termination. If this resistor has drifted high, the video will be overly bright and “blown out.”

Section_4: MODERN CONSOLE FAULTS (HDMI & POWER RAILS)#

Scenario: PS4, Xbox One, or Nintendo Switch specific failures.

STAGE_4: 01 // The “WLOD” (White Light of Death / No Video)#

• The System: Sony PS4 / PS5.
• The Check: Inspect the HDMI port pins for mechanical displacement.
• Forensic Step: If the port is physically perfect, probe the HDMI Encoder IC (Panasonic/MN series).
• The Test: Check the 4 tiny EMI filters next to the encoder for continuity. If an EMI filter is “open,” the digital differential pair is severed.

STAGE_4: 02 // Nintendo Switch “No Charge” Logic#

• The Check: Measure the M92T36 charging IC.
• The Short-Check: Test the capacitors surrounding the M92T36 for shorts to ground.
• Forensic Clue: A shorted cap here usually indicates the IC has been “blown” by a non-compliant USB-C cable or charger that sent 15V into a 5V sensing line.

STAGE_4: 03 // HDMI Retimer Logic (PS4 Pro / PS5 / Xbox Series)#

• The System: Systems using dedicated Retimer ICs (e.g. SN75DP159 or MN864731).
• The Check: Set the Multimeter to Diode Mode. Red probe to Ground, Black probe to HDMI data pins.
• Forensic Clue: All four differential pairs (Pins 1, 3, 4, 6, 7, 9, 10, 12) should show a reading of approx. 0.500V – 0.700V.
• Analysis: An “OL” (Open Loop) reading on a pin suggests a blown Retimer IC or a cracked solder joint under the BGA package.
• The Power Check: Verify the 1.1V Core Rail and 3.3V IO Rail reach the capacitors adjacent to the Retimer. If 0V is detected, the fault is “Upstream” in the PMIC, not the Retimer.

STAGE_4: 04 // PS5 Liquid Metal Forensics (Thermal Shutdown)#

• The System: PlayStation 5 (CFI-10xx through CFI-12xx).
• Symptom: Console shuts down instantly during PS5-native games, but functions fine in menus or PS4 titles.
• The Check: Visual inspection of the APU surface and the heatsink contact plate.
• Forensic Clue: Look for “Dry Spots”—grey, dull patches on the silicon die where the liquid metal (Gallium-Indium alloy) has oxidised or pooled due to vertical orientation.
• The Fix: utilised a cotton swab soaked in 99.9% IPA to gently scrub the oxidation from the die surface. Re-spread the existing liquid metal or apply 0.1g of fresh Conductonaut.
• Technical Warning: Ensure the internal Foam Dam is 100% intact. A single droplet of liquid metal escaping the dam onto the surrounding SMD capacitors will cause a catastrophic, un-repairable short.

Section_5: AUDIO FLOOR FORENSICS#

Scenario: Video is perfect. System plays fine. Audio is missing, distorted, or hum-heavy.

STAGE_5: 01 // The “Hiss” Test#

• The Check: Turn volume to max.
• Analysis A: Total Silence = Dead Audio Amp or missing +9V/+12V rail to the Amp IC.
• Analysis B: Low Hiss/Buzzing = Pre-amp logic is functioning, but coupling capacitors are dried out (Common on Game Gear/PC Engine).

STAGE_5: 02 // Headphone Jack “Ghosting”#

• The System: Handhelds (GBC, GBA, GG).
• The Check: Insert and remove a 3.5mm jack 10 times.
• The Logic: The internal physical leaf-switch gets stuck in “Headphone Mode,” muting the speaker even when unplugged.
• The Fix: Direct injection of DeoxIT D5 into the jack housing followed by mechanical cycling.

Section_6: THE “REBOOT/STABILITY” PROTOCOL#

Scenario: Console works for 10-20 minutes, then crashes or resets.

STAGE_6: 01 // Thermal Runaway#

• The Check: Measure the temperatures of the CPU and Regulators using a thermal camera.
• Practical Note: On the Nintendo 64, dried-out thermal pads prevent heat transfer to the aluminium blocks. The RCP will thermally “hang” to prevent self-destruction.

STAGE_6: 02 // ESR Load Failure#

• The Logic: As capacitors heat up, their Equivalent Series Resistance (ESR) changes.
• Diagnostic: A capacitor that measures “borderline” at 20°C may fail at 50°C internal case temperature.
• The Fix: A preventative Full Recap is the only “Heritage Logic” solution for stability issues in 30-year-old hardware.